Apparatus for the dimpling of hard metal alloys



cfi. 4, 194-9. 2,483,798

APPARATUS FOR THE DIMPLING OF HARD METAL ALLOYS H. E. VEIT 2 Sheets-Sheet 1 Filed Aug. 4, 1944 INVENTOR. HEP/WWW E VE/T d 4/. fw z;

A TTORNEY Oct. 4, 1949. H. E. VEIT APPARATUS FOR THE DIMPLING OF HARD METAL ALLOYS 2 Sheets-Sheet 2 Filed Aug. 4, 1944 IN VEN TOR. HERMAN E'. VE/T' ATTORNEY Patented Oct. 4, 1949 UNITED srA-T as PAS]! em orFli-oe.

APPARATUS FORTI-IE DEMPLING 0F mm!)- METAL ALEGYS Hermann. E. Veit, Tnwson, M'deuassignor to: The: Glenn L. Martin-Company, Middle RivemMdw acorporatiorrof Maryland Applicationlitugust 4, 1944, Serial No. 5483073 5. Glaimsr .11

My invention is directed to a methodandiap paratus for forming dimples; and, morexparticuvlarl'y; to a methodand apparatus-fer the dimpling of hard metals and hard metal alloys;

It is customary; lathe-construction" of aircraft; and of other" items of manufacturewhere the riveting of metal is'required; to employtheart or flush riveting. In" theaircraftindustry this prac ti'ce is'essential fortlie attainment of aerodynamic smoothness ofthe exterior surface; a factor vitally afiectin'g the" speed and maneuverabiliwof the plane.

The conventionalmethod of flush riveting is'to dimple the sheets of material about each rivet hole. This operationplaces a dimple or depression; around a hole for thereception. ofvthe head of the rivet so that the. top of the r'ii/et'head will be: flush with the surfaceot the In the dimpling. or. most sheetmetals the. tool of my earlier Patent No. 2,288 ,3781 has beenfouncl satisfactory. Certain alloys,- however, 0i aluminum and of magnesium which have been foundfio. be very advantageousior aircraitin thatthey presenttthe desired qualificationsinrrespect to weight. and tensile strength, are presently of limited utility only because of; the difficulty of dimplingt the. material: Thus; thosehig h-istrengtlr alumi num: alloys which are more brittle than aheat treated, rolled sheet of an alloy of 4.5% copper,- 0.6% manganese; 1.5% magnesium and: 93A aluminum-anurrently standard structural alloy, denominated by one large producer as '24S'l3--= cannot be uniformly and satisfactorily dimpledi' by any known tooilor'methodlat aratethat would examplaan alloy 01% 3 aluminum; 1% zinc; 012% manganese, and- 953% magnesiumL-cannot be: satisfactorily dimpled with knowntools, such asthat of'imy earlierfBatent-No; 2,2882378} without? preheating of the: sheet.

Such materials would be widel y'us'ed inthe -air cr'aftindustry today if theywere capaile ofsatisfactor dimpling' on a productionbasis. 'Itisan object of my invention, therefore, to develop a method and apparatus: of; producing dimples'in' such materialsas well' as others, one-production basis, and without any requirement ofpreheating;

It isafurth'er object of my invention to: provide a method and apparatus for the production in rivet -seating sheets- 0f a: dimpled depression-hav ing a: size: and a; shape that-will? conform closely to; the sizeand shape of therivethead; an'd w-hich rivet-t-seatii:ig sheets to produce a dimple with sharp corners at the periphery: instead the.- corners are. under: the present practice rounded by reason of the forming action employed inpro- 'ducihgtlie dimple; This leaves an opening or crack around the head of the rivet, which not only affects the airflow; but whichinducesconrosion as we'll;

Ihis rounding, of the corner results from the nature of the di'mpl'ing operation currently'employed, which consists simply of depressing" the work between forming; dies or tools. This iseffected without spinning; and; without any anprecia'ble flow, of the metal of the sheet; present. invention,,however, relates to the use of a forming, spinning and burring tool which p'erforms three distinct but cooperative. operations in the. shaping, of the. dimple The metal around the rivet hole is depressed and stressedlliy thesame axially oi the opening. This is accomplished; simultaneously. by aiorming and by a. spinning operation. As the metal forming. andspinning element of.v tool is rotated it progressively works: the metal downwardlyintortheshape of thedimple; thinning; the metal slightly inthe dimpled portion. In-this operation there isa tendency to. form a burner ridgeat. the juncture; between: the; plane of the sheet and the? periphery of the-dimple. A burrer immediately shaves or cuts'awaythisridgeAeaving. the corner sharp; clean; and flush. with the" rivet: headwhenit is inserted.

Ingenera'l, theserandzother object'sareachieved; according: to my invention by my use of the. close cooperation. its time: and betweem the axiali deformatiom of the metal; the spinning of theunetal; and therburrmgmperationn Thelnecessity forthis' combination; of. functions arises: from the age hardeningcharacteristics:of'metali Itds well; lmown: that aiterra' pieceof metal is worked amagehardening-takes place; so that the-hardness characteristicsrof: the metal vary fromthe instant after it is worked for a period of hours or.- days thereafter; If the axial working; thespinningv of the metal, and theiburring thereof were separate operations-performed independentlyon each rivet hole in" eachsheet, all of the dimples, and the burrs raised by the spinning, would be variously workhardened and age liardened'before the final will provide a sharp corner at the juncture lie 55 hurting operation tool: place.

My invention, however, permits the completion of each dimple in a single operation, and the time factor between the spinning and the burring of each dimple is a constant. This will eliminate the danger of variations or inaccuracies in the burring operation because of the different qualities of the metal.

The nature and operation of my apparatus will appear more fully in the accompanying drawings, wherein:

Figure 1 is a cross-sectional view of my dimpling tool, with the work in place on the anvil portion;

Fig. 2 is an enlarged endview of the spinning and burring elements of the tool;

Fig. 3 is a fragmentary detail showing the lower portion of the dimpling tool;

Fig. 4-. is a cross-sectional view of a sheet of material having a dimple formed therein according to prior art methods;

- Fig. 5 is a cross-sectional view of a sheet of material having a dimple formed therein according to my invention;

Fig. 6 is a cross-sectional view of an alternative form of the anvil portion of my dimpling tool; and

Fig. 7 is an enlarged fragmentary perspective View showing the spinning, burring, and pilot elements of the tool.

A preferred form of the apparatus of my invention comprises a rotating body I having at one end a spindle 8 adapted to be secured to and driven by the chuck of a conventional drill press 8A, and an anvil 9 maintained by a depending centering boss ID in a suitable fixture or vise 9A in alignment with the axis of the body. The lower end of the tool body I is provided with an axial bore H internally threaded to receive the threaded shank [2A of a metal spinning element l2. The element I2 is formed near its upper end with a transverse shoulder l3 adapted to fit closely against the lower end of the toolbody. At its lower end the spinning element i2 isformed with a plurality of radial ribs it each having a rounded outer edge shaped to spin the material surrounding a hole in a metal sheet into the conical recessed upper end 33 of anvil 9 forming the dimple.

die. Surroundingthe spinning element below the shoulder l3, and in threaded engagement with the spinning element, is a burrer l5 formed at its lower end with a bevelled cutting edge It positioned to remove the burr formed around themriphery of the dimpled area as the metal surrounding rivet hole 39 is displaced by the radial ribs 14 during the spinning operation. A shim I"! may be inserted between the shoulder l3 and the burrer l5 to permit necessary adjustment of the latter to compensate for wear. Thus when the cutting edge It becomes worn, the shim Il may be replaced by a thicker one to effect the necessary adjustment. This adjustment may be so regulated that the cutting of the burr takes place as the spinning of the dimple is being completed. This permits an unskilled operator to produce uniform, unscored dimples.

The spinner i2 is formed in its lower end with a hollow axial bore i8 adapted to receive the shaft IQ of a pilot 2!), threaded or otherwise secured in the bore.

I have found it desirable'to form the tool body I of an ordinary tool steel, and to use a very hard material for the spinner l2 and burrer 15, since these are used in the forming of the dimple and in the cutting of the burr formed around the pe riphery of the dimpled area by the spinning element l2 while dimpling the sheet W. It is, of

.4 course, obvious that a single body of hard material might be used alternatively to supplant the combination of the body, the spinner and the burrer which I have shown. The advantage of the preferred arrangement, which is here shown and described, is the reduced expense due to the use of a cheaper metal in the body, in the ease of replacement of either the spinner or burrer when they become worn or damaged, and in the convenient means of adjustment of the burrer through use and substitution of the shim II.

I employ, in my present invention, a slidably mounted cylindrical pressure pad 2! having an axial bore for the major portion of its length and the work. V

No. 2,288,378, this slight flexing of the materialupwardly prior to forming the dimple eliminates the depression which would otherwise form in the area adjacent the dimple. Where sheets greater in, thickness than about .040 of an inch are be--' ing dimpled, according to the instant invention, I have found that the sheet will be strong enough to withstand the downward pressure occasioned by the spinning, and the pressure pad 2| may be omitted.

To guard against rotation of the pressure pad,

which bears upon the surface of the metal being worked, I employ thrust bearings 25 about the.

tool body I.

A holder 26 comprises a collar 27 extending around a reduced upper end portion of the tool body and two depending arms 28 adjacent the body and secured at their ends to the pressure pad as by screws 29. To prevent binding of the collar on the body the parts may as at 30.

The anvil 9 is provided with a convex upper surface 3! which is complementary to the concave surface 22 on pressure pad 2!,and which cooperates with the lower surface of the pressure pad in the ore-flexing of the material, as above described. The anvil is formed with a centrally located bore 32, flared outwardly at its upper end 33 to provide the die for the dimpling operation.

To remote the shavings from the burring operation I have provided holes 34 in the wall of the pressure pad 2! adjacent an annular channel 35 and a tapped hole 36 for the attachment of an air line 37, connected to a source of air which may be adapted automatically to supply air pressure whenever the dimpling device is in its raised position. A handle 38 of any conventional form may be secured onto one of the holder arms 28 to prevent rotation of the pressure pad while the tool is in operation, to avoid damage to the work in the vicinity of the rivet hole.

In certain installations the handle may not be required and where it is omitted the dimpling tool will rotate freely while it is in its raised position. In this case the centrifugal force will be sufficient to remove the burr shavings through the holes 34, and the air line attachment will be unnecessary. When the tool is lowered into contact with the Work W, the frictional engagement between the work and the pressure pad 2! will be sufiicient to prevent the further rotation of the dimpling tool until it is again removed from be chamfered assesses like. metal spinning element; 1 22 is; its. lower 'endi of a generally-conical: shape; and is here shownas formedi with three radial: ribs; M. which accomplish: the working: of thametal; The ribs have a.- lesserradius: of" curvature than; that of the conical elementfrom VhiChLthBy are formed, as shown in Fig. 7- The-conical surfaee'is indie catedias lla. Asshown in..E'ig;.*Z,' theleading and trailing edges or the ribs. I t are curved to: reduce the amount: of friction. resulting from: the spin:- ning operation and: prevent. the. gouging: of. the metal by: therotatin ribs; the. spacing between the ribspermitsthe flow of the: metal as his being'worked', whereas. an unribbed conical piece would provide no relief to accommodate such a flow.

The operation ofthe. dimpling. toolmy invention is as follows:

The work W to be dimpled is provided with a rivet hole- 39- anvd placed iii-positionon the anvil 9. The: dimpling tool is. then lowered tad-place the pilot. 211 through the; rivet. hole directly over the: bone: 32 of the anviL The; spring: 23 forces the pressure pad 2| against the work coaxially withthe rivet hole 39. The; work is thus; first held and bent slightly upwardly around'theedges ofithe rivet hole. As the downward pressure: is continuedthe spring 23- is: compressed and the ribs I54 ofthe metal spinning. element l2: and the bevelled cutting edges l6 of the burrer l move vertically through the opening in the pressure pad 21. The increasing pressure of the rotating metal spinning element simultaneously frictionally engages the uppermost surface of the area to be dimpled, and forms the material into the die recess 33 of the anvil 9. As a burr is formed at the upper edge of the dimple, the rotating cutting edge 5 immediately removes it, forcing the shavings into the channel 35, whence they will subsequently be removed by air pressure from the air line 31 or by centrifugal force. The extent of the burring operation is controlled by use of the shim IT.

The ribs l4, here shown as three in number, will in actual operation be controlled, both as to configuration and number, by the amount of friction necessary for the dimpling of the material involved. If heat is required for the dimpling of the material, the friction may easily be increased by using a metal spinning element having either a greater number of ribs or less rounded embodying ribs, and thereby presenting a greater surface of contact. My invention, as shown and described, permits the easy replacement or substitution of either the spinner or the burrer, whether for the purpose of varying the nature of the dimple, for working a different quality material, or for the replacement of worn or broken parts.

My tool makes possible the dimpling of materials heretofore believed to be unsuited to this operation. In addition, by its combined spinning and forming function, it eliminates the round corners 42 previously unavoidable (Fig. 4), and produces quickly and efficiently a sharp cornered dimple 43 having walls 44 slightly thinner than the surrounding material, (Fig. 5). A further advantage of a dimple of this character is that it permits a nesting of the dimples where like sheets are stacked one upon the other.

The construction and arrangement of the parts as herein described is such that it requires no high degree of skill on the part of the operator to make uniformly satisfactory dimples. The predetermined relative adjustment of the spinning element and the burring edge limits the r 6 extent" of the, spinning operation and permits the cutting of the burrf'as the." elementisbotttomerhin; anvil, thus avoiding the" danger of cutting too. deeply ina removing the burr.

In, Fig; 6:1 have an. alternative formof anvil; Imthiswmodiflcation L1 have. providedan improved, meansafor quickly" centering the rivet hole to: he. dimpled over the dies portion of the anvil: is frequently a: time. consuming: operto center material exactly; yet it; is extremely vital that: this aligmnenti bev exact" to avoid; crack-ingot thedimplesr and injury to; the dimpling: toolsa.

Accordingito'my invention. I have provided: an anvil having. a hollowbody '45: open. at the: bot.- tom and} threademinteriorly to receive a. plug 41%: carried; Ona aa'basei 41' from which is" depended a centering boss 43. Resting on.a;sp1:ing:4.9: witlrthe liollovvbody isv a head 50 at one end' of plunger." 51 passing through art axial bore 52 of; theranvil body to. protrude beyond thenpper face: thereon. In; operation this device: works; as

follows:

The Work W is. placed: over the: anvil with its rivet hole 39 aligned; withzthetplunger 517.. As the dimplingitooii is lowered thea pilot: 23. is centered on the plunger 5i". and: thereatter pressess-the plunger downzinto the anviiabody; thereby -'remnv'- ing it: tromi-thea bore duvin'g'the: dimpling. operation.

When the pilot is again removed the plunger is free to rise, thereby regaining its position for guiding and centering the dimpling tool in the next operation.

I claim:

1. A tool for dimpling hard sheet metal stock comprisin an anvil having a conical recess and. a coaxial pilot bore, means adapted to be moved toward and away from said anvil comprising a pilot to center the stock with respect to said bore, a rotatable metal spinning member rotatable about the axis of said pilot to spin the stock to be dimpled into the conical recess of said anvil as the pilot is advanced with respect to said bore, work engaging .means located adjacent the outer periphery of the spinning member and adapted to press the sheet metal outside of the area to be dimpled toward the anvil, and metal cutting means carried by and adapted for rotation with said spinning member having a cutting edge placed parallel with the sheet surface to trim a flash or burr formed at the juncture between the surface of the sheet stock and the stock spun into the anvil recess.

2. A tool for dimpling an apertured hard metal alloy sheet comprising a supported convex surfaced anvil having a recess therein to form one face of a dimple in said sheet, a rotatable shaft adapted to be mounted in a rotating means, a spinning element having a plurality of radial ribs attached to said rotatable shaft and positioned to form a dimple in said apertured sheet to the shape of the recess in said anvil, a burr removing element carried by said rotary shaft and formed with a cutting edge adapted to rotate with the spinning element so as to efiect the removal of a burr formed around the dimple by the spinning element, a pressure pad carried by said rotary shaft having a concave surface formed outwardly of the spinning element to match the anvil and positioned to encircle, engage and flex the area to be dimpled surrounding said aperture placed in engagement with the anvil, and a passage formed in said pressure pad for the conduction of air to a point adjacent the spinning element.

3. A dimpling tool comprising an anvil, an apertured work engaging means adapted for movement toward the anvil having an engaging area aligned with said anvil to engage and secure under pressure work placed in engagement with the anvil for dimpling, a rotary dimpling means adapted for rotation within the work engaging means to dimple said work, burring means carried by the dimpling means and located at the outer periphery of the dimpling means provided with a cutting edge to remove a burr formed around the dimple during the rotation of said dimpling means in engagement with the work, a burr-shavings outlet means carried by said engaging means having a passage formed therein leading outwardly from adjacent the cutting edge for removal of burr shavings from within said engaging means.

4. A dimpling tool comprising an anvil for supporting a work piece, said-anvil, being formed with a conical dimple recess, a rotatable Spinning means formed with laterally projecting ribs and having a conical profile, said spinning means being mounted for advancement into the recess in said anvil, burring means carried by the spinning means and located at the outer periphery of said spinning means to remove a burr formed around a dimple insaid work piece.

5. A dimpling tool comprising an anvil for supporting a work piece, said anvil being formed with a conical dimple recess, a rotatable spinning means formed with laterally projecting ribs and having a conical profile, said spinning means being mounted for advancement into the recess in said anvil to form a dimple in said work piece, burring means carried by the spinning means and located at the outer periphery of said spinning means having a cutting edge to remove a burr formed. around the dimple in said work piece, and a pressure pad surrounding said spinning mean and arranged for movement to engage and secure a work piece on the anvil.

I-IERMANN E. VEIT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 14,878 Miller et a1. May 13, 1856 1,383,839 Mueller et al July 5, 1921 1,383,840 Mueller et a1 July 5, 1921 1,983,407 Scholtes Dec. 4, 1934 2,235,582 Klema Mar. 18, 1941 2,288,378 Veit June 30, 1942 2,308,447 Greenbaum Jan. 12, 1943 2,346,376 Heavener 'Apr. 11, 1944 

